1. Field of the Invention
The present invention relates to a circuit board of a solid-state image sensor for an electronic endoscope and, more particularly, to the structure of a circuit board to which a solid-state image sensor which is disposed in an electronic endoscope is attached.
2. Description of the Prior Art
An electronic endoscope apparatus is an instrument for inspecting internal cavities of the body by inserting an electronic endoscope, which is a scope, into an object of inspection such as an internal cavity of the body or a vomica and displaying the image of the object of inspection on a monitor. For example, a solid-state image sensor such as a CCD (charged coupled device) is mounted on one end of the electronic endoscope. FIG. 5 shows the structure of the end portion of such an electronic endoscope. As shown in FIG. 5, the end surface of an electronic endoscope 1 is provided with an observation window 2 for observing the object of inspection and picking up the image of the object therethrough, and a forceps insertion hole 3. A manipulating tool insertion channel 4 is provided so as to communicate with the forceps insertion hole 3, thereby making it possible to pick a tissue in a cavity of the body with a forceps or the like inserted into the manipulation tool channel 4.
An objective 5 is provided on the inside of the observation window 2, and a CCD 8 held by a package 9 is disposed at the following stage of the objective 5 through a prism 7. The CCD 8 is attached to the under surface of the prism 7 so that light which is refracted by the prism 7 enters the CCD 8. The CCD 8 is attached to the package 9 of a ceramic material by bonding wires, and the package 9 protects the CCD 8 from the influence of the environment such as heat and noise. The package 9 is attached to a substrate 10 composed of a rigid sheet by bonding wires. Signal cables 11 are connected to the substrate 10 and an electronic part is disposed thereon.
According to the above-described structure, the image of the object of inspection which enters the objective 5 through the observation window 2 is supplied to the imaging surface of the CCD 8, and the video signals obtained by the CCD 8 are output to the circuit formed on the substrate 10 and supplied to the processing unit in the main body through the signal cables 11.
Since the above-described conventional circuit board of the solid-state image sensor for an electronic endoscope is integrally connected to the CCD 8 and the package 9 by wire bonding, a circuit board having a suitable connection to an endoscope must be produced in correspondence with each type of endoscope. For example, with respect to the arrangement of the CCD 8, in a horizontal type endoscope, the CCD 8 is disposed in parallel to the axis of the endoscope (the direction in which light enters), as shown in FIG. 5, while in a vertical type endoscope, the CCD 8 is disposed vertically to the axis of the endoscope (the direction in which light enters). With respect to the position of the observation window, in a direct looking type endoscope, the observation window 2 is disposed at the front of the endoscope (in the axial direction), as shown in FIG. 5, while in a side looking type endoscope, the observation window 2 is disposed on the side surface of the endoscope 1 so as to observe the object of inspection from the side surface. In all of the above-described types, when the prism 7 is used, since light is reflected by the prism 7, the image is reversed side to side, and the connection between the CCD 8 and the substrate 10 must therefore be reverse to that in the case of not using the prism 7. Therefore, a circuit board which is produced for a certain type of endoscope cannot be used as a circuit board for another type of endoscope. In addition, in order to accommodate predetermined circuit parts within a narrow end portion of an electronic endoscope, the shape and the like of the substrate 10 must be changed. In such a case, the circuit board must be completely renewed.
An electronic endoscope is required to reduce the diameter of the end portion as much as possible. In the above-described structure shown in FIG. 5 , it is impossible to meet such demand sufficiently.